Christopher Smith
The minimal flavor violation hypothesis is presented in the context of the MSSM. Its fundamental principles are introduced and motivated, and its phenomenological consequences for FCNC and CP-violating observables as well as for R-parity violating processes are briefly described.
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This paper has been replaced as hep-ph/0003063 titled `Lepton flavor violation in the supersymmetric standard model with vectorlike leptons'.
We show there is a non-null probability to produce neutrinos of the ``wrong'' type in general decays, within the SM augmented by the known three massive neutrinos and nontrivial mixing. Such effect is equivalent to an intrinsic flavor violation (lepton flavor violation) at creation without requiring neutrino propagation. The exact amount of flavor violation depends on the neutrino flavor state to be detected. For realistic conditions, the violation is tiny but much larger than other indirect lepton flavor violation processes not involving neutrinos as final states. For neutrinos produced in a …
We show that in supersymmetric models with explicit flavor lepton number violation due to soft supersymmetry breaking terms there must be flavor lepton number violation in slepton decays. We propose to look for flavor lepton number violation in righthanded selectron and smuon decays. For selectron and smuon lighter than 80 Gev flavor lepton number violation in slepton decays could be discovered at LEP2 provided the mixing betwen selectron and smuon is not small. We also estimate NLC discovery potential of the lepton flavor number violation in slepton decays.
This dissertation investigates the flavor mixing effects in supersymmetric models on electroweak precision observables, Higgs boson mass predictions, B-physics observables, quark flavor violating Higgs decays, lepton flavor violating charged lepton decays and lepton flavor violating Higgs decays. The flavor mixing effects are studied in model independent way i.e. by putting off-diagonal entries in the sfermion mass matrix by hand as well as in the minimal flavor violating constrained MSSM, where mixing can originate from CKM matrix in the case of squarks and from PMNS matrix in the case of sle…
I discuss charged lepton-flavor violation in physics beyond the standard model and review topics related to it.
We present and discuss constraints on supersymmetric type I seesaw models imposed by neutrino data, charged lepton flavor violation and thermal leptogenesis.
We extend the notion of Minimal Flavor Violation to the lepton sector. We introduce a symmetry principle which allows us to express lepton flavor violation in the charged lepton sector in terms of neutrino masses and mixing angles. We explore the dependence of the rates for flavor changing radiative charged lepton decays (ell(i) -> ell(j) + gamma) and mu-to-e conversion in nuclei on the scales for total lepton number violation, lepton flavor violation and the neutrino masses and mixing angles. Measurable rates are obtained when the scale for total lepton number violation is much larger than th…
We show that in supersymmetric models with explicit flavor lepton number violation due to soft supersymmetry breaking mass terms there could be detectable flavor lepton number violation in slepton decays. We estimate LHC discovery potential of the lepton flavor number violation in slepton decays.
The exact discrete flavor symmetry, $S_3$ in the hadronic sector and $S_3 \times Z_2$ in the leptonic sector, which has been recently found, is introduced in a supersymmetric extension of the standard model. We investigate the supersymmetric flavor problem, and explicitly find that thanks to the flavor symmetry the dangerous FCNC processes and CP-violating phases are sufficiently suppressed.
We explore the effects of a strongly-coupled, approximately scale-invariant sector on the renormalization of soft supersymmetry breaking terms. A useful formalism for deriving exact results for renormalization of soft supersymmetry breaking terms is given in an appendix, and used to generalize previously known results to include the effects of nontrilinear superpotential terms. We show that a class of theories which explain the flavor hierarchy without flavor symmetries can also solve the supersymmetric flavor problem by producing nearly degenerate masses for the first two generations of scala…
In this paper we study flavor violation in supersymmetric models with gauged flavor symmetries. There are several sources of flavor violation in these theories. The dominant flavor violation is the tree-level $D$-term contribution to scalar masses generated by flavor symmetry breaking. We present a new approach for suppressing this phenomenologically dangerous effects by separating the flavor-breaking sector from supersymmetry-breaking one. The separation can be achieved in geometrical setups or in a dynamical way. We also point out that radiative corrections from the gauginos of gauged flavor…
An invited research highlight article on Charged lepton flavor violation searches in the charmonium system.
We discuss how neutrino oscillation experiments can probe new sources of leptonic flavor and CP violation.
In a generic supersymmetric extension of the Standard Model, there will be lepton flavor violation at a neutral gaugino vertex due to misalignment between the lepton Yukawa couplings and the slepton soft masses. Sleptons produced at the LHC through the cascade decays of squarks and gluinos can give a sizable number of events with 4 leptons. This channel could give a clean signature of supersymmetric lepton flavor violation under conditions which are identified.
Models of minimal lepton flavor violation where the seesaw scale is higher than the relevant flavor scale predict that all lepton flavor violation is proportional to the charged lepton Yukawa matrix. If extra vector-like leptons are within the reach of the LHC, it will be possible to test the resulting predictions in ATLAS/CMS.
The study for lepton flavor violation combined with the neutrino oscillation may provide more information about the lepton flavor structure of the grand unified theory. In this paper, we study two lepton flavor violation processes, $τ\to μγ$ and $Z\to τμ$, in the context of supersymmetric SO(10) grand unified models. We find the two processes are both of phenomenological interest. In particular the latter may be important in some supersymmetric parameter space where the former is suppressed. Thus, Z-dacay may offer another chance for looking for lepton flavor violation.
A minimal flavour violation hypothesis for leptons can be implemented essentially in two ways that are compatible with a type-I seesaw structure with three heavy singlet neutrinos $N$, and that satisfy the requirement of being predictive, in the sense that all lepton flavor violating (LFV) effects can be expressed in terms of low energy observables. The first realization is CP conserving and is based on the flavor group $SU(3)_e\times SU(3)_\ell\times O(3)_N$ (being $e$ and $\ell$ the SU(2) singlet and doublet leptons). The second realization allows for CP violation and is based on $SU(3)_e\ti…
Quark and lepton flavor signals are studied in four supersymmetric models, namely the minimal supergravity model, the minimal supersymmetric standard model with right-handed neutrinos, SU(5) supersymmetric grand unified theory with right-handed neutrinos and the minimal supersymmetric standard model with U(2) flavor symmetry. We calculate b --> s(d) transition observables in B_d and B_s decays, taking the constraint from the B_s--B_s-bar mixing recently observed at Tevatron into account. We also calculate lepton flavor violating processes mu --> e gamma, tau --> mu gamma and tau --> e gamma fo…
This talk discusses recent studies of (charged) lepton-flavor violation in physics beyond the standard model.
I review recent opportunities from flavor for b-physics and collider searches.
Minimal Flavor Violation in the up-type quark sector leads to particularly interesting phenomenology due to the interplay of flavor physics in the charm sector and collider physics from flavor changing processes in the top sector. We study the most general operators that can affect top quark properties and $D$ meson decays in this scenario, concentrating on two CP violating operators for detailed studies. The consequences of these effective operators on charm and top flavor changing processes are generically small, but can be enhanced if there exists a light flavor mediator that is a Standard …
We explore the possibility that the masses for the first two generations of fermions and the quark flavor violation are generated radiatively in the Minimal Supersymmetric Standard Model. We assume that the source of all flavor violation resides in the the supersymmetry breaking sector and is transmitted radiatively to the Standard Model fermion sector through finite corrections at low energy. The approximate radiative alignment between the Yukawa and soft supersymmetry breaking matrices helps to suppress some of the supersymmetric contributions to flavor changing processes, overcoming current…
We present a variant of the warped extra dimension, Randall-Sundrum (RS), framework which is based on five dimensional (5D) minimal flavor violation (MFV), in which the only sources of flavor breaking are two 5D anarchic Yukawa matrices. The Yukawa matrices also control the bulk masses, which are responsible for the resulting flavor structure and mass hierarchy in the low energy theory. An interesting result of this set-up is that at low energies the theory flows to next to MFV model where flavor violation is dominantly coming from the third generation. Low energy flavor violation is further s…
Theories of flavor violation beyond the Standard Model typically suppose that the new contributions must be small, for example suppressed by Yukawa couplings, as in Minimal Flavor Violation. We show that this need not be true, presenting a case for flavor violation which maximally mixes the first and third generation flavors. As an example, we realize this scenario via new right-handed gauge bosons, which couple predominantly to the combinations (u,b)_R and (t,d)_R. We show that this new flavor violation could be responsible for several anomalies, focusing in particular on the B_d and B_s syst…
Minimal Flavor Violation is an attractive approach to suppress unacceptably large flavor changing neutral currents from beyond the standard model physics at the TeV scale. It can be used in theories with low energy supersymmetry, multi Higgs doublet theories and other extensions of the minimal standard model. We show how minimal flavor violation can be implemented in Grand Unified theories.
Theoretical aspects of lepton-flavor violating (LFV) processes on the supersymmetric models are reviewed. In particular, we show that, assuming the minimal supergravity scenario, the LFV interaction at the higher energy scale leads to the the LFV processes, which may be accessible in near future experiments.
We examine some flavor changing processes such as rare leptonic decays of the long-lived neutral kaon, muon-electron conversion in nuclei and radiative muon decay which are induced by the combined effects of bilinear and trilinear R-parity violations. These processes are used to put strong constraints on certain products of the bilinear and trilinear couplings. We also discuss the constraints on R-parity violation from neutrino masses and compare them with the constraints from flavor changing decay processes. Large range of parameter space satisfying the constraints from neutrino masses can be…
Supersymmetric contributions to the neutron electric dipole moment (EDM) are studied taking account of the flavor changing interactions. We found that the gluino contribution is sensitive to the flavor changing interaction. Enhancement of neutron EDM via flavor mixing effects is possible when the squark mass difference between the different generations is sizable. As an example, the results of the SUSY SU(5) GUT with right-handed neutrinos are briefly discussed.
We consider the flavor structure of supersymmetric theories that can account for the deviation of the observed time-dependent CP asymmetry in B --> phi K_S from the standard model prediction. Assuming simple flavor symmetries and effective field theory, we investigate possible correlations between sizable supersymmetric contributions to b --> s transitions and to flavor changing processes that are more tightly constrained. With relatively few assumptions, we determine the properties of minimal Yukawa and soft mass textures that are compatible with the desired supersymmetric flavor-changing eff…
Clockwork models can explain the flavor hierarchies in the Standard Model quark and lepton spectrum. We construct supersymmetric versions of such flavor clockwork models. The zero modes of the clockwork are identified with the fermions and sfermions of the Minimal Supersymmetric Standard Model. In addition to generating a hierarchical fermion spectrum, the clockwork also predicts a specific flavor structure for the soft SUSY breaking sfermion masses. We find sizeable flavor mixing among first and second generation squarks. Constraints from Kaon oscillations require the masses of either squarks…
We show that new physics models without new flavor violating interactions can explain the recent anomalies in the $b\to s\ell^+\ell^-$ transitions. The $b\to s\ell^+\ell^-$ arises from a $Z'$ penguin which automatically predicts the $V-A$ structure for the quark currents in the effective operators. This framework can be realized either in a renormalizable $U(1)'$ setup or be due to new strongly interacting dynamics. The di-muon resonance searches at the LHC are becoming sensitive to this scenario since the $Z'$ is relatively light, and could well be discovered in future searches by ATLAS and C…
Lepton flavor violation at linear collider experiments is discussed. We show that detectable lepton flavor violation could occur through scalar lepton pair production and decay in the supersymmetric SU(5) grand unified theory in spite of the stringent present experimental constraints by rare process searches. Possible cross sections about 40fb for an e+e- collider and 280fb for an e-e- collider are illustrated.
We present a class of supersymmetric models in which flavor symmetries are broken dynamically, by a set of composite flavon fields. The strong dynamics that is responsible for confinement in the flavor sector also drives flavor symmetry breaking vacuum expectation values, as a consequence of a quantum-deformed moduli space. Yukawa couplings result as a power series in the ratio of the confinement to Planck scale, and the fermion mass hierarchy depends on the differing number of preons in different flavor symmetry-breaking operators. We present viable non-Abelian and Abelian flavor models that …
We investigate the maximal approximate flavor symmetry in the framework of generic minimal supersymmetric standard model. We consider the low energy effective theory of the flavor physics with all the possible operators included. Spontaneous flavor symmetry breaking leads to the approximate flavor symmetry in Yukawa sector and the supersymmetry breaking sector. Fermion mass and mixing hierachies are the results of the hierachy of the flavor symmetry breaking. It is found that in this theory it is possible to solve the flavor changing problems. Furthermore baryogenesis of the universe can be we…
Recent results from Super Kamiokande suggest $ν_μ-ν_τ$ mixing and hence lepton flavor violation. In supersymmetric models, this flavor violation may have implications for the pattern of slepton masses and mixings. Possible signals for this mixing in the decays of sleptons produced at the LHC are discussed. The sensitivity expected is compared to that of rare decays such as $τ\to μγ$.
I study many higgs doublet supersymmetric model with spontaneous CP violation. The damaging flavor changing interactions and large CP violation are brought under control simultaneously by an approximate PQ symmetry. I relate the smallness of the CP violating parameter in the kaon system to the small ${m_b \over m_t}$ ratio.
Now the bounds on the lepton-flavor violating (LFV) decay modes of tau lepton are being improved by the Belle experiment in the KEK B factory. In this paper the LFV decay of tau lepton is discussed in the supersymmetric seesaw model, using the current neutrino oscillation data.
I review briefly the notion of minimal flavor violation and its application to supersymmetry, with a special emphasis on a class of operators, so-called Higgs penguins, which can generate new and interesting flavor signals at large tan(beta).
We study the one-loop supersymmetric contributions to lepton-flavor violating $Z$ -boson decays in a fully left-right symmetric model. In addition to right-handed scalar neutrinos, the decays could receive important contributions from doubly-charged triplet Higgsinos which couple to leptons only. We find that the decay widths reach present experimental bounds and discuss mass constraints for the contributing supersymmetric partners.
Lepton flavor violation in various sectors of the theory can bring important effects on neutrino masses and mixing through wave function renormalization. We examine general conditions for flavor structure of radiative corrections producing the atmospheric and solar neutrino mass splittings from degenerate mass patterns. Also obtained are the mixing angle relations consistent with the experimental results.
Supersymmetric theories generally have new flavor violation sources in the squark and slepton mass matrices. If significant lepton flavor violation exists, selectron and smuon should be nearly degenerate. This leads to the phenomenon of slepton oscillations, which is analogous to neutrino oscillations, if sleptons are produced at the Next Linear Collider. The direct slepton production at the Next Linear Collider provides a much more powerful probe of lepton flavor violation than the current bounds from rare processes, such as $μ\to eγ$.
We analyze the lepton-flavor violation in supersymmetric models with non-universal soft breaking terms derived from strings. We show that the non-universality of the scalar masses enhances the branching ratios more significantly than the non-universality of the A-terms
Supersymmetric theories generally have new flavor and CP violation sources in the squark and slepton mass matrices. They will contribute to the lepton flavor violation processes, such as $μ\to e γ$, which can be probed far below the current bound with an intense muon source at the front end of the muon collider. In addition, if sleptons can be produced at the muon collider, the flavor violation can occur at their production and decay, allowing us to probe the flavor mixing structure directly. Asymmetry between numbers of $μ^+ e^-$ and $e^+ μ^-$ events will be a sign for CP violation in supersy…
It is shown that intrinsic neutrino flavor violation invariably occurs when neutrinos are created within the SM augmented by the known massive neutrinos, with mixing and nondegenerate masses. The effects are very small but much greater than the naive estimate $Δm^2/E_ν^2$ or the branching ratio of indirect flavor violating processes such as $μ\to eγ$ within the SM. We specifically calculate the probability (branching ratio) of pion decay processes with flavor violation, such as $π\to μ\barν_e$, showing nonzero results.
We construct a renormalizable, supersymmetric theory of flavor and $R$ parity based on the discrete flavor group $(S_3)^3$. The model can account for all the masses and mixing angles of the Standard Model, while maintaining sufficient squark degeneracy to circumvent the supersymmetric flavor problem. By starting with a simpler set of flavor symmetry breaking fields than we have suggested previously, we construct an economical Froggatt-Nielsen sector that generates the desired elements of the fermion Yukawa matrices. With the particle content above the flavor scale completely specified, we show…
Heavy singlet neutrinos admit Majorana masses which are not possible for the Standard Model particles. This suggest new possibilities for generating the masses and mixing angles of light neutrinos. We present a model of neutrino physics which combines the source of lepton number violation with the flavor symmetry responsible for the hierarchy in the charged lepton and quark sector. This is accomplished by giving the scalar field effecting the lepton number violation a nonzero charge under the horizontal flavor symmetry. We find an economical model which is consistent with the measured values o…
The high-energy astrophysical neutrinos recently discovered by IceCube opened a new way to test Lorentz and CPT violation through the astrophysical neutrino mixing properties. The flavor ratio of astrophysical neutrinos is a very powerful tool to investigate tiny effects caused by Lorentz and CPT violation. There are 3 main findings; (1) current limits on Lorentz and CPT violation in neutrino sector are not tight and they allow for any flavor ratios, (2) however, the observable flavor ratio on the Earth is tied with the flavor ratio at production, this means we can test both the presence of ne…
We discuss potential to measure squark flavor mixings based on future data at super B factory and LHC. In particular we focus on the imaginary part of the mixings by investigating the CP violating observables. As a result, we find they are determined with the uncertainty about 10 % at best.
CP violation can be observed in B decays when a given process depends upon interference between two weak amplitudes which have different $CP$-violating phases. Since most weak decay diagrams have quark lines where each has a definite flavor label, neutral mesons which are flavor mixtures are particularly interesting. Different diagrams can contribute to the different flavor components of the meson, and the wave function itself provides interference.
Flavor mixing and the quark mass spectrum are intimately related. In view of the observed strong hierarchy of the quark and lepton masses and of the flavor mixing angles it is argued that the description of flavor mixing must take this into account. One particular interesting way to describe the flavor mixing emerges, which is particularly suited for models of quark mass matrices based on flavor symmetries. We conclude that the unitarity triangle important for $B$ physics should be close to or identical to a rectangular triangle. $CP$ violation is maximal in this sense.
We examine the lepton-flavor violation caused by a Yukawa coupling matrix $y_{ν,ij}$ for right-handed neutrinos in the supersymmetric standard model. We stress that decay rates for $τ\rightarrowμγ$ and $μ\rightarrow eγ$ may reach the range to be accessible to near future experiments if left-right mixing terms in the slepton mass matrix are substantially large.
The mixing between third and second (or first) generation squarks is very small in supersymmetric models with minimal flavor violation such as gauge-, anomaly- or gaugino-mediation. An opportunity to measure this mixing will arise if the lightest stop is close enough in mass to the lightest neutralino, so that the decays into third generation quarks are kinematically forbidden. We analyze under which circumstances it might become possible to measure at the Large Hadron Collider (LHC) the rate of the flavor changing stop decays.
In this lectures, we give a review about the Minimal Supersymmetric Standard Model (MSSM) with $R$-Parity Violation because it provides an attractive way to generate neutrino masses, lepton mixing angles in acconcordance to present neutrino data.
If new physics is called upon to explain away fine tunings, like the hierarchy problem, then, we argue, the principle of Minimal Flavor Violation is inescapable. We review the principle and recent extensions to the lepton sector and to Grand-Unified theories.
Supersymmetric standard models where the ultraviolet cut-off scale is only a few orders of magnitude higher than the electroweak scale are considered. Phenomenological consequences of this class of models are expected to be very different from, for example, the conventional supergravity scenario. We apply this idea to a model with an anomalous U(1) gauge group and construct a viable model in which some difficulties of the decoupling solution to the supersymmetric flavor problem are ameliorated.
We discuss flavor charges and states for interacting mixed neutrinos in QFT. We show that the Pontecorvo states are not eigenstates of the flavor charges. This implies that their use in describing the flavor neutrinos produces a violation of lepton charge conservation in the production/detection vertices. The flavor states defined as eigenstates of the flavor charges give the correct representation of mixed neutrinos in charged current weak interaction processes.
Issues of proton decay are examined in supersymmetric standard model with U(1) flavor symmetry. Dimension five proton-decay operators which arise generically are controlled by the flavor symmetry. We show that unlike the minimal supersymmetric SU(5) case the proton decay modes containing charged lepton can have large branching ratios if the dimension five operators of left-handed type dominate. Measuring the branching ratio of the electron mode to the muon mode may reveal the mechanism of the neutrino mass generation. The case with vanishing charges for Higgs doublets marginally survives the p…
Neutrino oscillation experiments suggest existence of new flavor-violating interactions in high energy scale. It may be possible to probe them by the flavor- and CP-violating processes in leptons and hadrons in the supersymmetric (SUSY) models. In this article the third-generation flavor violation is reviewed in the SUSY seesaw model and SUSY SU(5) GUT with the right-handed neutrinos.
We study contributions of supersymmetric CP phases to the CP violation $ε'/ε$ in models with asymmetric $A$-matrices. We consider asymmetric $A$-matrices, which are obtained from string-inspired supergravity. We show that a certain type of asymmetry of $A$-matrices enhances supersymmetric contributions to the CP violation $ε'/ε$ and the supersymmetric contribution to $ε'/ε$ can be of order of the KTeV result, $ε'/ε\sim 10^{-3}$.
Lepton flavor and CP violation in supersymmetric models are briefly reviewed. After a short motivation and an introduction to the phenomenology, model independent constraints on mass insertions, predictions of SUSY GUT models and rates for several LFV and CPV processes are presented.
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